1. Field of Invention
The present invention relates to a sense circuit. More particularly, the present invention relates to a current sense circuit for current-mode DC/DC converters.
2. Description of Related Art
In a conventional current-mode controlled DC-to-DC (DC/DC) converter, a current sense circuit including operational amplifiers (OP) provides a sensed current based on a load current. By utilizing the operational amplifier, a scaled current can be acquired from a power transistor and generated through a dummy transistor.
However, the operating voltages of the power transistor and the dummy transistor are usually very low, so the input of the operational amplifier still has to be kept at a low voltage/current level while the operational amplifier is supposed to operate at a high speed appropriately. The operational amplifier also needs compensation as well such that the operational amplifier cannot operate at the high speed as expected. As a result, the current sense circuit fails to provide the sensed current correctly.